Numerous studies have been conducted in the past using patent statistics to explain and compare the innovative forces of districts, regions and countries. The usual method of calculating the regional distribution of patent counts - not only in Germany but in many countries all over the world - is to assign the patents to districts by inventors' residential addresses. This is considered more appropriate than assigning the inventions by the address of the applying company which, in the case of larger firms' headquarters, holdings or subsidiaries, can be very misleading in geographical terms. It is commonly agreed that this method, due to the streams of commuters, leads to an underestimation of the innovative activities in the agglomeration - an issue that has, to our knowledge, never been proven. In this paper we suggest two ways that may help to get a more realistic picture of the regional distribution of innovation activities in the future and even, with hindsight, for past data. (c) 2005 Elsevier B.V. All rights reserved.